In general, a small-sized camera module is mounted in mobile terminals such as a smartphone. The lens driving device has an auto focus function of automatically performing focusing for capturing a subject (hereinafter referred to as “AF (Auto Focus) function”), and a shake correction function (hereinafter referred to as “OIS (Optical Image Stabilization) function”) of optically correcting hand shake (vibration) upon capturing an image to reduce the irregularities of the image (for example, PTLS 1 and 2).
The auto-focusing and shake-correcting lens driving device includes an auto-focusing driving part (hereinafter referred to as “AF driving part”) for moving the lens part in the light axis direction, and a shake-correcting driving part (hereinafter referred to as “OIS driving part”) for swaying the lens part in a plane orthogonal to the light axis direction.
The AF driving part includes, for example, an auto-focusing coil part (hereinafter referred to as “AF coil part”) disposed around the lens part, and an auto-focusing magnet part (hereinafter referred to as “AF magnet part”) disposed separately from the AF coil part in the radial direction. An auto-focusing movable part (hereinafter referred to as “AF movable part”) including the lens part and the AF coil part is moved with respect to an auto-focusing fixing part (hereinafter referred to as “AF fixing part”) including the AF magnet part in the light axis direction by use of a driving force of a voice coil motor composed of the AF coil part and the AF magnet part, and thus focusing is automatically performed. The AF movable part and the AF fixing part are collectively referred to as “auto-focusing unit (AF unit).”
The OIS driving part includes a shake-correcting magnet part (hereinafter referred to as “OIS magnet part”) disposed at the AF unit, and a shake-correcting coil part (hereinafter referred to as “OIS coil part”) disposed separately from the OIS magnet part in the light axis direction, for example. A shake-correcting movable part (hereinafter referred to as “OIS movable part”) including the AF unit and the OIS magnet part is supported by a supporting member so as to be separated from a shake-correcting fixing part (hereinafter referred to as “OIS fixing part”) including the OIS coil part in the light axis direction. The OIS movable part is swayed in a plane orthogonal to the light axis direction by use of a driving force of a voice coil motor composed of the OIS magnet part and the OIS coil part, and thus shake correction is performed.
Further, PTLS 1 and 2 disclose a configuration in which the same magnet part is utilized as an OIS magnet part and an AF magnet part from the viewpoint of reducing the size and the height of the lens driving device. The magnet part serving as the OIS magnet part and as the AF magnet part is referred to as “driving magnet part.”
In addition, PTL 2 proposes a configuration in which: a Hall device is disposed at an AF fixing part; a position detection magnet is disposed at an AF movable part; the position of the AF movable part is detected with the Hall device; and the operation of a voice coil motor of the AF driving part is controlled based on the detection result (so-called closed loop control method). With the closed loop control method, the hysteresis characteristics of the voice coil motor are not required to be considered, and stability of the position of the AF movable part can be detected. Furthermore, automatic focusing of the image surface detection method can be used. Accordingly, with high responsiveness, speedup of the automatic focusing operation can be achieved.